The Institute of Electrical and Electronics Engineers (IEEE) has adopted a set of standards for wireless local area networks (WLANs), known as 802.11, as well a set of standards for wireless metropolitan area networks (WMANs), known as 802.16. Wireless products satisfying the 802.11 and 802.16 standards are currently on the market, for example. The term, WiFi, describes equipment satisfying the 802.11 standard. The term, WiMAX, short for worldwide interoperability for microwave access, describes equipment satisfying the 802.16 standard.
Currently being developed is an 802.16m standard, known also as “4G”, “LTE-advanced”, (where “LTE” means “long-term evolution”) and “advanced air interface”, which supports data rates of 100 megabits/second mobile and 1 gigabit/second fixed. Under the advanced air interface standard, heterogeneous networks, or “overlay networks”, with potentially different cell sizes or even different radio access technologies (RAT) may be co-located in the deployment. This gives an extra degree of freedom for mobility and cell selection optimization, which was previously only based on the downlink signal strength.
Thus, there is a continuing need to provide optimal mobile station support as it travels through a heterogeneous overlay network.